What to Expect During a Pet Scan

A PET (positron emission tomography) scan is used to detect changes in the tissues and organs of your body. X-rays, CT scans, and MRIs show the shape and structure of your body’s organs and tissues. A PET scan shows how they work. A PET scan uses small amounts of radioactivity, called a radionuclide, to take detailed pictures of different areas inside your body.
A small dose of this radionuclide is injected into a vein in your hand or arm. The radionuclide gives off positively charged energy particles, or positrons. The PET scanner rotates around the body to detect these positrons at many different angles.

If you become uncomfortable lying still for a long time or if you are uncomfortable with close spaces, talk to your doctor beforehand. Arrangements can be made for you to receive a sedative before your scan. If you have a sedative, you will need to inform the receptionist and take medication one half hour before the scan to take the medication. If you have a sedative, you must have someone to drive you home.

Preparing for Your PET Scan

  • Do not eat or drink for 4 hours before your appointment.
  • If you need to take medications, take them with a small sip of water.
  • If you have diabetes, contact your physician for specific instructions. You may need to follow special guidelines. Do not take insulin for 4 hours before your scan.

The Day of Your PET Scan

  • Plan to report to the imaging center on time. The dose of your radionuclide is made precisely for the time of your appointment.
  • If your brain is being scanned, you will need to wait quietly, usually in a dimly lit room. You will need to avoid any mental stimulation such as reading or talking
  • If other areas of the body are being scanned, you will be able to read, listen to music, etc.
  • You may spend 2 to 3 hours at the imaging center. The actual scanning time is anywhere from 20 to 60 minutes. The time can vary depending on the number of areas being scanned that day.
  • A soft, flexible tube or needle will be inserted into one of your veins. You may feel a brief sting in your arm when the IV is inserted. The radionuclide will be given to you through this tube.
  • You may need to wait about 60 minutes for the radionuclide to move through your body.
  • You may be asked not to speak during the procedure in order to prevent the radionuclide from going to your tongue or vocal cords.
  • You will be placed on a flat table that moves through a donut shaped opening on the PET scan machine. The scan makes no noise.
  • During the scan, you will need to lie very still because any movement could interfere with the test results. The table moves and glides you through the machine, so you do not need to move.

After Your PET Scan

  • If you were not sedated, you may leave as soon as the scan is complete.
  • Unless you receive special instructions, you may eat and drink immediately and go back to your usual activities and diet.


  • No side effects are associated with the radionuclide tracer.
  • The tracer is eliminated rapidly from your body, making it safe for you to be near others during and immediately after a PET.